Fix attachment filename with no extension

NEWS

@@ -8,6 +8,9 @@ Enhancements
  - [core] avoid showing bundle loading info when not needed (#3726)
  - [core] when restoring data using sogo-tool, regenerate Sieve script (#3029)
 
+Bug fixes
+ - [web] fixed crash when an attachment filename has no extension
+
 2.3.12 (2016-06-10)
 -------------------
 

UI/MailPartViewers/UIxMailPartViewer.m

@@ -270,7 +270,7 @@
   if ([filename length])
     // We replace any slash by a dash since Apache won't allow encoded slashes by default.
     // See http://httpd.apache.org/docs/2.2/mod/core.html#allowencodedslashes
-    filename = (NSMutableString *)[filename stringByReplacingString: @"/" withString: @"-"];
+    filename = [NSMutableString stringWithString: [filename stringByReplacingString: @"/" withString: @"-"]];
   else
     [filename appendFormat: @"%@-%@",
 	      [self labelForKey: @"Untitled"],